I had 2 tourist visas I got a blue stamp after the first tourist visa. Also one land crossing and extension while waiting for documents. I had been on a non b Visa for about 13 months before that. It's a language school in BKK no real problems with other applicants. I found out later that they are looking at the length of time your are in Thailand even if your on the right visa before hand. I got a blue stamp after 1 tourist visa and everytime they point to it and I try to explain but they don't listen. Wrong place wrong time. I have friends with
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tourist visas and then got a ED visa no problems. I think alot had to do with new rules and the new appointment system being brought in, alot of people from Vientiane went to Savannakhet around the time. I ve heard its a lot easier at Kota Bharu. My school have been sending people there and had success. Good luck.