mine actually did go beyond my thirty day stamp…. Immigration folks told me not to worry because I had the “under consideration” stamp in my passport. The visa finally came about 10 days past the thirty day stamp. Again, this was in Chiang Mai.
Be aware that Chiang Mai frequently takes longer than 15 working days. Just a heads up in case you’re planning to leave the country soon after the day you expect to get it. Mine took almost a month when I applied in November here in CM.
As others have noted…it’s all doable. However, if you come in on a 30 day visa exempt entry, get to the immigration office right away as there is an under consideration period. You want that under consideration period to end before your 30 days are up. Depending on the office, it may be three weeks so…hop right on it!
Have you considered converting to an “O” visa from the “O-A”? Sure, you need funds on deposit but if you plan to spend a long time in Thailand it may be better for you than paying for “less than good” insurance. Just a thought!