Your best choice is to obtain a multiple entry Non-Immigrant visa which valid for 12 months. With this visa type you will need to exit and enter Thailand at least every 90 days to get a new entry stamp allowing you to stay a further 90 days.
If you utilize your visa the last time just before it expires, you will get an extra 3 months “bonus”, so the total validity will be nearly 15 months.
You will probably NOT get a Multiple entry visa in neighboring countries, your best chance of getting it is in your home country before you arrive in Thailand.
Thai consulates in US, Europe and Australia seem to be the most generous. The smaller consulates in Australia are the nearest and the easiest, and air tickets to there are cheaper than to Europe or North America. A return ticket from Bangkok to Australia can be bought for less than 25,000 Baht.
The Royal Thai Consulates in Adelaide, Brisbane and Perth in Australia issue Multiple entry visas, as per September, 2003, we are informed.
If you are married to a Thai citizen, you can easily get a multiple entry visa in Penang. Bring your Thai marriage certificate in original (and one copy) and check out our forum for more details.
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