In Malaya, the troops, who were far forward to launch Matador got hit by fresh Japanese troops who had full ammo, full food, full everything. They got crushed and the British supplies went to the Japanese. Percival should, have at this point, pulled way back and scorched the earth behind him, but he didn't. He kept on setting up defensive lines near the Japanese where they could both move troops fast enough to get behind and then hit him at full strength.
In Burma, it was even worse. The British troops were right on the border. THey were trying to defend airfields, but what they were effectively doing was serving up green troops of the Indian Army and Burma division to be slaughtered. Their next defensive point was ... in front of a river. and not very far back. Rather than defending with the river at their front... they put it right on their back and were forced to blow the bridge when the Japanese attacked with half of the British forces still on the Japanese side.
Well, I think it needs to be said that the quality of the individual infantryman was also a major factor. The Indian soldiers, especially the Jats, Rajputs and the Madras regiment gave what can only be called an abysmal performance (It needs to be noted that the soliders probably didn't identify with the British empire and for them it was probably a pointless foreign war). The British officer corps and the few ethnic British units in the theatre also shown incopetence, lack of discipline, low moral and low fighting skills.
In contrast, the Punjab regiments fought in an adequate manner, while the Australians, Gurkhas and the Nigerians proved to be above-average.
But all in all, the individual Japanese infantryman proved to be a far superior soldier than the individual Indian or British infantryman. This was a major factor in the outcome of the war in that theatre, even deep down in 1944 where the Japanese supply situation had deteriorated to a pitiful level.
I don't mean to say that Percival or Stillwell were good commanders, they were not. But A lot of the blame lies with the low quality British and Indian troopers in the ranks. Percival was part and parcel of that army as a whole.
Regarding Percival, I read that under his command, pamphlets on fighting tanks remained neatly stored in the offices because doctrine said that the peninsula were not suitable for tanks (just like the Ardennes I guess) and so the pamphlets probably surmounted to heresy or something.
Would they have made a difference?
Did the amateurish-style British officer in the Indian army have the necessary military skill and education to make use of advanced tactical doctrines? Doubtful. Did he have the intelligence, popular respect and language skills to pass this on to his Indian troops? Certainly not.
The Indian and British rank and file were not part of the problem, they were THE problem. Even Nigerian troops (The British command initially doubted their capacity and treated them as secondary forces) proved much more efficient.
I also read, that he refused to recruit civilian labor for much needed fortification works, first giving no reason and when pressed explaining, he feared it would be bad for morale.
It very well might have been. The local Malay population was not friendly towards the British. Malaya was certainly less mismanaged than say Bengal, but it was very badly mismanaged nevertheless. The population, save maybe ethnic Han urban middle class, had absolutey no reason to be loyal to the British (and indeed would later assist the Japanese in many cases).
I would like to point out that Percival only had to defend a predefined position with ample time to prepare, while the Japanese had to attack. Given their logistical situation, simply delaying them could feasibly have collapsed their forces, as happened later at the Burmese/Indian border in 1944.
True, but for that would require soldiers that were willing to stand and fight, probably take serious losses. The Indian forces would retreat from one position to another because the alternative was to have them brake and run entirely. The Empire simply lacked the high-morale manpower that would be dedicated and loyal to it.