I've overstayed for 43 days once, though was not entirely my fault - the revenge of the former employer - but just paid 20,000 baht and was reprimanded by a female officer a little bit. Though, the overstay was discovered when I was extending my new working visa, not while applying for one. I still don't know how it wasn't discovered when I had applied for a new Non-B visa in Vientiane...