Definitely Gurkha.
I recognise the SBO and cap from those Gurkha I met in Ubin.
Basically there were scattered groups of threes or fours of these
people hiking. They were unarmed, wearing the DPM trousers, boots,
SBO, cap and shirtless!
At first I thought they were Mat punk rockers on a hike. They look
no older than sixteen.
Or Bruneians NCC cadets.
The jockey cap really threw me off for, like everyone, I thought
they wear the folded hat or jungle hats.
When I saw a second similarly dressed group I got curious and asked
them where they are from and they said Gurkha.
The uniform is British DPM. It is worn by our Gurkha but also by
the Bruneians. Malaysia doesn't wear British DPM.