usually it depends on how many are ahead of you - they process them 1st come 1st served...unless you go in person and slip them a few Baht- magic happens then - wow.... or they have no control but will take your money anyway and you will get approval as soon as all the others ahead of you are completed....lol
CDN here - I was in thailand and went to india - you need to go to the india embassy and present your passport and they will take it and process it - for me was 3 hrs. with a stapled in visa + $$