So I wanna ask you all, what should I do when my boss keeps asking me to work overtime all the time?

I'm 22, I'm the only accountant in a small branch of our company in Nakhon Ratchasima. Been here almost a year. Normal hours are 8:30–17:30 but lately he keeps calling me in. Sometimes I have to get there before work actually starts, like 6:45am, to check documents. Other days I get home almost 9pm because I have to close reports for other teams — it's really starting to affect my life. My mental health is bad, I'm sleepy every afternoon around 2–3pm and I can't nap at work lol.

Short version: my boss likes getting me to do after-hours stuff, like organizing his personal files or running to the copy shop at 7pm (all the little shops on the side street are closed so I have to find it myself). I go because I think it'll score me points, but after almost two months problems have started. If a document has a small mistake he'll yell/complain in front of other department colleagues and dodge responsibility, even though I worked late. Other people in other teams don't help — they dump it all on me and stay quiet.

I can't take it. I'm so confused.

I once tried to talk politely: "I'd like to stick to my contracted hours." He replied, "Just help out, don't be difficult." So I kept agreeing because I'm new and want to survive, afraid of looking bad. But there's this voice telling me not to keep doing this or it'll break me. I feel like I'm everything to everyone and they'll keep taking advantage. Am I overthinking? Is this normal for small companies where everyone just has to put up with it? Or how should I set boundaries?

Another thing is my salary isn't high. If I say no I'm afraid it'll hurt my performance review, and I'll lose chances for raises. I honestly can't figure out whether to endure it for the future or be blunt before I burn out in 1–2 months. I don't want to be the bad guy but I also don't want to be a tool.

Some nights when I get home late I pass by the noodle stall on the corner I like and wonder if life is worth trading for time. But then in the morning I still go to work like normal, I'm so confused about myself. Am I just being sulky? T_T

If any of you have been through this or are accountants, real advice — what exactly should I say? Please tell me straight phrases I can use, like how to speak politely but firmly so I don't get labeled lazy. If I set up a formal meeting with my boss, should I state specific hours and limits like I can only work until 17:30 or ask for at least 24 hours' notice? Is that okay, or should I start job hunting instead?

P.S. If anyone has exact short sentences to use when asked to work overtime, please type them out. I have a little blue notebook to practice so I won't choke when I actually talk. I'm really scared but gotta do something, what should I do?