Be persistent. Because the truth about tuna, especially the kind for human consumption(and they shouldn't even eat cat food tuna exclusively either) is that it's empty calories. Cats rely very highly on their sense of smell to be attracted to their food. They actually have a relatively poor sense of taste compared to people. Tuna is very smelly and often the stuff that smells most offensive to people, cats love. Tuna fish doesn't even have the nutrients that cats need, can cause vitamin E deficiency leading to yellow fat disease, and while it is high in protein, that is not enough. Cats need a lot of vitamins and minerals in their diet and they need those in the right ratios and proportions. They especially need taurine for their heart and their vision. Without taurine they will go blind and eventually die of heart failure. Tuna fish for human consumption is very low in taurine. There is also much concern about mercury levels in tuna that can be harmful to both cats and people if too much of it is eaten. Tuna can be fed to cats occasionally as a treat as long as they don't become addicted to it to the point where they don't eat anything else. Unfortunately your cat is a tuna junkie. You will need to take her to the vet if she continues to starve herself. In the meantime here are a few things you can do.
To get her on cat food, try buying fishy cat foods that are formulated to be nutritionally complete, containing all vitamins, minerals and taurine that the cat needs. One food to try for cats that are really finicky and stubborn is Fancy Feast. And while there are people here who will say that Fancy Feast is not the highest quality food you can feed, Fancy feast which is formulated to be nutritionally complete is better than tuna. And plenty of cats have lived long on this type of junk food anyway. In fact often when a cat has a reduced appetite a vet will ask, "Have you tried Fancy Feast?" If you don't have Fancy Feast in Thailand, then try Friskies, 9 lives, whatever it takes to get her eating. Once she is eating those you can try buying cat food cans that contain some fish but also contain other ingredients such as chicken, turkey, beef or lamb. You may not be able to get your cat completely off fish but the important thing is to get her to eat cat food. Has your kitty been eating anything at all besides tuna? For example, dry cat food? Not that cats need dry cat food, canned food is actually better for them, but dry cat food, even the fish flavored dry cat foods are better for your cat than tuna fish simply because the vitamins and minerals and taurine are in there.
Most importantly don't let your cat go more than 48 hours without eating. If this happens, take her to to the vet. She may be sick.