Hi!Welcome to Miata-Thai.net.
Here is to answer your questions...
If you stay close to Pattanakarn area, I would suggest you to Jub Garage. The owner, K.Jub, he is another Mx5 specialist in BKK. He does all the fixing and also a very well known HKS F-Con tuner !He can do all type of car set-up eg. 4 throttles,superchargers and turbo chargers. Of course he also do all standard cars' check up and overhaul engines.
Call him and consult him. His mobile phone no. is 089-8947915
Cheers !!