as a Filipino citizen she gets 60 days visa exempt on arrival, she can then extend 30 days more. The same goes for you if your nationality is allowed visa exempt on arrival. 93 countries has this so I assume you’re of one of those nationalities?
Immigration usually don’t care about your return ticket, airlines do.
I always have a bus ticket from Thailand to Cambodia 250b booked with a date previous to my 60 days expire just in case someone asks.