Plenty of travellers arrive for a month and want to stay longer. There are proper ways to do it, and one very bad one.
Apply for a longer visa up front
The simplest option is to choose a 90-day visa when you first apply, if you have any suspicion the trip may stretch. Upgrading later is harder than deciding early.
In-country extension
Extensions are handled through the immigration department and generally require a sponsoring agent. Start the process at least a week before your current permission expires, not on the final day.
Exit and re-enter
Some travellers leave to a neighbouring country and return on a fresh visa. This works, but it needs a new e-visa arranged in advance — you cannot rely on sorting it at the border.
What overstaying costs
Fines are charged per day and settled at the airport on departure, which is exactly when you have the least time to deal with it. In serious cases it affects future entry.