Call On Cloud is operated by Mail Master Co., Ltd., a provider of Cloud PBX, SIP Trunk, and Voice AI Agent services for businesses, regulated by the NBTC, serving more than 4,500 organizations nationwide.
Who We Are
Call On Cloud is the phone systems and business communications brand of Mail Master Co., Ltd. We run a full PBX stack — Cloud PBX hosted on AWS Bangkok, on-premise IP PBX deployments, and VoIP hardware distribution — backed by a team that designs, installs, and supports the system for the life of the deployment.
We operate as a licensed VoIP provider in Thailand under NBTC oversight, an authorized reseller for leading IP phone and networking manufacturers, and a business-number partner alongside the country's major telecom carriers.
Numbers, SIP trunk, the PBX itself, endpoint hardware, and Voice AI Agent all sit under one contract and one support team — no chasing multiple vendors when something breaks.
We run our telecom business under NBTC oversight and issue contracts and tax invoices as a registered company, ready for the procurement process at any enterprise or government agency.
Thai-speaking, familiar with Thai business context, and staffed by the same team after the sale — not an overseas call center.
Every service we run sits on a proper license, hardware from manufacturers who appointed us as their reseller, and network capacity from the country's major carriers.
Voice-over-internet service in Thailand is a licensed activity. Choosing a provider inside that regulatory system lowers your organization's compliance risk directly. To confirm: license number and type held
Appointed reseller for IP phone and networking equipment manufacturers.
Business phone number reseller.
Our Story
Mail Master Co., Ltd. was founded in 2016 out of a problem we saw clearly — corporate email is hard to run well, full of small operational details, and at the time few providers in Thailand understood it deeply enough to be responsible for an enterprise-grade system.
“We solve the problems everyone else finds too messy to take on — from email, to phone systems, and today to Voice AI Agent. Every time we expand, we hold to the same standard: own the whole system, don't just sell the product.”
We were among the first providers in Thailand to run a clustered email system on AWS To confirm: the “first” claim, and we've continuously supported peak concurrent usage above 20,000 users. Our outbound mail (SMTP) infrastructure uses a multiple-IP design and manages reputation across 85+ IPs to keep inbox delivery as high as possible. To confirm: a defensible deliverability figure
We deliver and implement email on Google, Microsoft, and Zoho — all three platforms — so we can support almost any organizational setup, whether migrating, running a mixed environment, or building from scratch. That same expertise is the foundation we bring to phone systems and Voice AI Agent today.
Our Services
Beyond the Call On Cloud brand, Mail Master Co., Ltd. is also a reseller and IT service provider across several other categories — so you can handle more of your IT needs with a single partner.
Reseller and service provider for Google, Microsoft, and Zoho business email, on-premise and cloud, including setup, migration, security, and deliverability management.
Benefit: Migrate email without disrupting daily work, with a team accountable when messages don't arrive.
Enterprise software licensing and management — Microsoft Windows, Microsoft Office, Adobe, Foxit, Kaspersky, and Bitdefender.
Benefit: Legitimate, auditable licenses, with documentation ready for internal audit and procurement.
Reseller and advisory for software-as-a-service tools such as email marketing, transactional email, and e-signature platforms.
Benefit: Tools chosen for the actual business problem, with a team to help design the solution and connect it to existing systems.
Office and enterprise hardware delivery — Dell, HP, Brother, Lenovo, and ASUS, plus IP phones and networking equipment.
Benefit: Hardware, network gear, and IP phones specified to match the system we already installed.
Product Portfolio
Two service groups that work together on a single system — enterprise phone infrastructure, and AI that can genuinely answer calls for you.
From business numbers and SIP trunk to the PBX itself, call recording, and AI call summaries.
Thai-language AI agents that work with Cloud PBX, designed around PDPA and data-leak prevention from the start.
Mail Master has grown steadily among Thailand's business email providers, and has ranked as a national top reseller for both Microsoft 365 and Zoho Mail licenses. To confirm: the year and ranking criteria
What we track above revenue is the renewal rate — infrastructure services like email and phone systems prove their quality in year two and three of use, not on the day the contract is signed.
National Top Reseller, Thailand
National Top Reseller, Thailand
Enterprise customer renewal rate
XX%Client Growth Trend
(2016–2025)
Our Clients
From SMBs to large enterprises, hospitals, logistics companies, retail, media, insurance, and government agencies.
Client names shown only where permission has been granted. To confirm: rights to use each company's name/logo, and its official name
Why Call On Cloud
We sell services your business relies on every day, so our pitch isn't a feature list — it's confidence that the system keeps running on your busiest day.
The platform is hosted on AWS Bangkok Region (ap-southeast-7); call data and recordings never have to leave the country.
Set access rights, retain logs, and define a data-retention policy the way your legal and IT security teams require.
Reach the team that installed your system directly, without re-explaining the setup every time you open a case. To confirm: support hours/response-time SLA
We've handled migrations, CRM integrations, and procurement requirements in enough different shapes to flag risk before a project even starts.
Uptime and remedy terms are written into the contract and auditable, not a verbal promise. To confirm: uptime SLA figure
A properly appointed provider, lowering compliance risk when procuring telecom services.
“We believe every day, everything should get a little better — whether that means improving how we work, or how we handle a problem.”
That management philosophy is what got the company to where it is today, and it's the standard we use to decide what comes next. Every problem a customer runs into feeds back into how we operate — it doesn't just get closed as a ticket.
FAQ
Call On Cloud is the phone systems and business communications brand operated by Mail Master Co., Ltd. All contracts, quotations, and tax invoices are issued under Mail Master Co., Ltd. (Tax ID 0105559065799).
Yes — we provide VoIP service in Thailand under NBTC oversight. If your procurement or legal team needs supporting documentation, we can provide a copy of the license. To confirm: license number and type held
On AWS Bangkok Region (ap-southeast-7), inside Thailand — which makes cross-border data transfer questions under PDPA straightforward to answer. Retention periods are set according to your organization's policy.
Yes — our support and engineering team is entirely Thai-based. Reach us by phone at 02-028-7722, LINE @calloncloud, or email; support level and hours depend on the package selected. To confirm: support hours and response-time SLA per tier
Yes. We serve both private-sector and government clients, and are familiar with the documentation procurement requires — company certification, conditional quotations, spec comparison documents, and compliance paperwork.
In most cases we can port your existing numbers and migrate users in stages without a service interruption. Our team surveys the existing system and equipment and plans the cutover with your IT team before work begins. To confirm: standard installation timeline