I have always applied for extensions in the same location that I have my TM30 (that may not be a requirement). I think you can get several if you felt the need. I mean, go to Phuket and get a new TM30. The hotels are suppose to do that for you so you may want to check with them. Different Immigration offices have different policies about when you can apply for extension so you can plan based on that. Last extension I got was in December from Phuket,
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day process.