In Korat it takes from sending the form on the website to receiving the automated confirmation about 30 minutes to max. 2 hours. The approval comes usually on the next working day about 11 a.m., attached the sticker for the passport as PDF. I never wait until the last day. The IO sends a reminder 14 days before due day and I just go the Immigration website and do the form. All data is prefilled, just put in your passport number and nationality and click the magnifier. This seems to be the first official website which really works. It saves me a round-trip of 180 kms every time the 90 days are due. Great service, Thank You, Immigration.