Yep I know you are looking at Patong but if you wanted to consider outside Patong with a car rented as well then take a look at where Dman and myself live
The Kamala Hills Apartments, probably one month in peak could be secured for 50k or less but would need to know for certain in the near future and then could have a word with a few local owners to ensure booking for your dates.
Quite tidy, safe, well serviced, cheap to live in for elec etc, most are 3 bed, some have own splash pools but there are 4 community pools on the development anyway.
Kamala is 12km away from Patong 15 mins by car or mbike, just thought it might be option as you wanted 3 rooms so thought maybe coming with family or partner, if 3 lads too far from action maybe???.