Working in the O&G as project engineer for 3 years with relatively very low pay compared to market. Now got transferred internally to Maintenance sector as Maint. Engineer with still the same pay.

Typically o&g pay dont increase as fast as what others tink.

If you feel that gaining more experience in the Maintenance sector will benefit your long-term career prospects, then following your peers' advice might be a good option. After all, it will look better for resume to stay in the same company for 5 years with 2 roles, compared to staying in the job 3 yrs at 1 role. However, if you believe that seeking opportunities with higher pay elsewhere is more important to you at this time, then exploring other companies could be the right move. If you feel that theres no room for growth or your passion lie elsewhere, it is good to take the leap and find another job.

Think being transferred usually should have better salary, think 3 years means experienced too

Internal transfer rarely result in pay increment unless there is an obvious promotion or up in rank.

Agree with 1M45, just apply! If got offered a higher pay job, just jump! If not, just hang around to "learn the ropes".

BTW, who are the peers advising you? You sure they are genuine in helping or more for sabotaging?