The west coast refers to the coast of the Gulf of Thailand, west of Bangkok.
Starting at Cha-Am beach. 25 km to the south is the rich beachs of Hua Hin.
Drive south to Hiway 3167 turn west to Burma border town of Dan Singkhon. A good market for gifts from Burma.
Then to Bang Saphan. Not so good beaches, but pretty ocean views.
Futher south is Chumphon. They spoke only Thai at the hotel and resteraunt, but welcomed foreign visitors.
Then south and across to the Indian Ocean is Phuket, a well established international beach.