My dear sister Chelsea
Being myself a 19 year old cradle Catholic, I’m not entirely familiar with the actual procedures and process of RCIA, having never gone through it myself. However I know that its quite a length process of learning and discernment. You will be a Catechumenate for roughly around a year, I think, if my memory serves me right. Usually Catechumens are received into the Church at Easter.
You can, of course, attend Holy Mass whenever you like! You do not have to be a baptized Catholic to attend Mass, which is open to everyone who seeks it.
However, I would see how this works with your parents first. I wouldn’t want there to be an friction or arguement caused between you all, unnecessarily. Ultimately you are an adult and must make your own decisions, and your parents have to respect this. If you want to go to Mass, then you should go to Mass because its your right to freely discern your own path in life.
Your desire to become Catholic means that you are, already, in essence a Catholic. Baptism by desire is sufficient to make one a child of the Catholic Church. So my advice is: Don’t sweat it

Take your time, read, pray and inquire. Make sure that you really do want to become Catholic and learn, learn, learn.
Also see this:
"…You find yourselves in a world where the majority of your fellow citizens embrace Buddhism, that complex of religious beliefs and philosophical ideas which is rooted in Thai history, culture and psychology, and which profoundly influences your identity as a nation…As people of Thailand you are heirs of the ancient and venerable wisdom contained therein.
How can you as Christians, members of the Catholic Church, who recognize Christ as the Saviour of the world, respond to Christ’s call of discipleship, living, as you do, immersed in a religious environment different from your own?
Sacred Scripture gives insights for an answer to this question. The second reading from the Letter of Saint James speaks of an earthly wisdom which is opposed to “the wisdom from above”, which is pure, peaceable, gentle, open to reason, full of mercy and good fruits, without uncertainty or insincerity. Your cultural heritage as Thai people is intimately linked to the indigenous Buddhist tradition, which provides a fertile terrain for the seed of God’s word, proclaimed by Jesus Christ, to take root and grow. In the practice of Buddhism can be discerned a noble tendency to strive to separate oneself from an “earthly wisdom”, in order to discover and achieve an interior purification and liberation…Here too, as people who are enriched by the Buddhist tradition of your country, you are endowed with a special sensitivity to the renunciation of violence in the vindication of personal rights, and so the Lord’s injunction to be peacemakers strikes a resonant chord in your minds and hearts, helping you not to fall victim to the many temptations to violence that haunt the world…"
- POPE JOHN PAUL II (Homily) National Stadium of Bangkok (Thailand) Thursday, 10 May 1984