There where in fact about 70,000 Japanese and Thai troops involved in the Battle, not 30,000.The Japanese kicked the bejesus out of the British in Asia. Anyone uncertain of that fact can have a look here:
140,000 British troops surrendered to a mere 30,000 Japanese soldiers.
Not to mention the fact the Japanese had three times as many Aircraft and better ones at that, over 200 tanks to the British zero tanks. And the Japanese troops where tough well trained veterans(The Japanese Guard division was used in Malaya) while many of the British troops where untrained recruits from India or second line rear area troops.
It was still a great victory for the Japanese, but as one British General said(Forget which one) Its not as important who wins the first Battle of a war as who wins the last Battle