Once a Thai bank account gets locked for dormancy, you usually have to visit a bank branch in person to reactivate it. This is largely a security measure, partly to prevent fraud if the account holder has passed away. Simply trying to perform a transaction remotely to reactivate the account typically won't work. Also, for foreigners, many Thai banks no longer allow you to maintain an account unless you hold a long term visa and can provide proof of residence in Thailand. On top of that, some banks charge maintenance fees on dormant accounts, amounting to few hundred Baht a month. If you leave an account sitting with only around 4,000 Baht left in it, those fees can completely wipe out your balance after a couple of years. There is also an older thread on this topic here in case it might be of interest:
