Dear Khun Varoon_sak,
I have made not so good experiences with MTH when using Roco Multimaus or Fleischmann Profi-Boss and would recommend to use the following steps to find out the root cause:
1. Was the locomotive working when you tested it at the shop?
2. What controller was used at the shop to test it for you? (MRC/Roco/Fleischmann?)
3. If you bring the locomotive back to the same shop now, is it still working?
From my experience, the only solution was to send back the locomotive to the US and get it replaced (and possibily paying 20%+7% tax again) and sent back to Thailand again.
Best is always to approach the seller in the first place.
Hope I was able to help.