In general, do revolutions need the support of the populace to achieve long-term success?
No. Not at all. It's a nice bonus. Nothing more. Plenty of dictatorships ruled with very little popular support. Thailand is not an exception to the rule. It only happens more often than elsewhere.
I can only say: welcome to Thailand! In the 25 years that I live here about 3 successful (military) coups have been committed and several failed (civilian) attempts. In the west children look in winter for the weather forecast, hoping the school might be closed. Thai children watch the news. Perhaps another coup closes the school!
Since 1932 at least 40 coups have been committed. All 'in the name of the people'. Conveniently forgetting the previous military government did exactly the same thing. In Thailand, it is usually the army (sometimes the police, rarely any other branches) who commit coups. The support they have comes from the army. And of course, some of 'the political elites'. Definitely not the people.
Actually, the coup that ousted premier Thaksin Shinawatra in 2006 was the first coup in Thai history where the coup-makers gained widespread popularity!
Thaksin himself was the first Thai politician who kept most of his electoral promises to gain popular support. That in itself was unique in Thai history. He was, and still is, very popular amongst the (mainly rural) people. No other politician had done that before him. (Nor after him, for that matter.)
In general, do revolutions need the support of the populace to achieve long-term success?
No. Not at all. It's a nice bonus. Nothing more. Plenty of dictatorships ruled with very little popular support. Thailand is not an exception to the rule. It only happens more often than elsewhere.
The first coup, the revolution that abolished the absolute monarchy in 1932, was committed by princes and ranking nobles who felt passed over for promotions. All in the name of the people, of course.
The current "civilian" government is the previous junta, who all retired from the army. Premier Chan-o-Cha committed his coup in 2014. He postponed elections many times until 2019. He's ruling 6 years with many to come. Pretty long by Thai standards.