I just returned from 10+ day leisure trip to Thailand. Some days in BKK and some days the South (Nakhon Si Thammarat).

Nakhon Si Thammarat area was largely unaffected from the virus. Very few wore masks - if they did, it was from traffic air pollution I think. However, I just heard from local friend that recently an infected person has been found in Nakhon - apparently, he/she returned from Iran.

BKK: Notably fewer visitors in the city, especially from China. Hotel rates very low now. Fewer guests in restaurants, bars etc. No need to book ahead for massage etc. No queue at immigration at the airport. It is clear that Thai tourism is seriously hurt; many complaining about low business. Many wear masks when outside, in BTS and busses etc - may also be related to the current high air pollution (2.5PM was 100-150). Bring masks and hand sanitizer from home.