@Alex *********
For the one year extension there is no criminal background check. Yes, visit your immigration office for the list of requirements.
Careful about your insurance. The insurance that qualifies you for the visa may not qualify you for the 1 year extension. These companies will qualify
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Getting your non Thai Cigna insurance to qualify may be a problem.
I generally recommend that people get an O visa these days. Then you can keep your Cigna insurance for sure.