Hello!
I have a DT 200i and have similar problems to yours. I live in Singapore so similar weather condition to Malaysia (hello neighbour!).
In the morning, and only the morning, I start bike for first time. Starts perfectly and sets into normal idle, no issues. I ride it out on my condo basement car park and towards the condo gantry, max maybe 70-100meters. All good. When approaching gantry I start to coast for the first time and approach a stop for the first time at which point the engine would normally go back to its 1500rpm idle. However it doesn't, it goes down to 1000rpm and struggles occasionally just cutting out as the idle cannot sustain (sometimes it just manages to hang on and goes up to 1500rpm. Problem doesn't;t happen again). If it cuts out, restarting the bike is then difficult, cranking for 3-5 seconds to get it going, sometimes blipping the throttle to help it. I ride on and the problem never happens again (so I assume the engine warmed up ever so slightly resolving it??).
I read your posts and it sounds similar. Can you confirm what the issue was? My bike is 2015 DT200i. Only 19400km on clock. Well serviced. I just replaced air filter, oil filter, oil, spark plug, transmission oil, and that has not solved anything. I tried the TPS reset procedure many times, doesn't make a difference. I wonder if it is a sensor given that it only happens when cold and after a very brief period it never happens again (so warmed up). But frankly don't know.
Thanks for any comments!
Richard