Director General of the Department of Disaster Prevention and Mitigation (DDPM) Phasakorn Boonyalak said the Cell Broadcast System (CBS) will undergo a test run next month in localised areas including the sprawling capital, which was badly shaken by the 7.7-magnitude quake in neighbouring Myanmar.

The system will use three mobile networks to send warning messages "quickly and with wide coverage, both on natural disaster and security threats", he told a news conference.

Starting on May 2 with the smallest target area -- four city hall buildings -- there will be three test runs, with the third and largest drill covering the whole of Bangkok and Chiang Mai provinces on May 13.

Residents' cellphones will get a pop-up message on their screens in Thai and English, accompanied by a siren, Phasakorn said.

The message will read: "This is a test message from Department of Disaster Prevention and Mitigation, no action required."

Phasakorn said it was CBS's first public test run and that tourists on roaming networks would also receive the alert.

The DDPM aimed to get alerts out within 10 minutes of an earthquake, he said.

The March 28 quake killed more than 3,700 people in Myanmar and at least 53 in a tower block under construction in Bangkok that collapsed dramatically.

While Thailand rarely experiences such strong tremors, Bangkok often experiences heavy flooding in the rainy season.