Note the non-standard spelling -- with a 'k' rather than a 't' at the end of the first syllable of strictly.In fact, this accurately represents the real pronunciation of this word, not just in Brunei but throughout the world. Nobody usually pronounces the [t] in strictly, because that would involve the three-consonant sequence [ktl], which is pretty hard to say.
So maybe this sign writer is ahead of their time; perhaps this is how we will all be writing this word in a few years time. Just like most people nowadays write hiccup rather than the traditional hiccough, because hiccup accurately reflects the way we say the word.
On the other hand, maybe the traditional form strictly will prevail, because it maintains the morphological link with strict. In this case, it is similar to Christmas and handkerchief which always seem to maintain the 't' and 'd' in the spelling even though [t] and [d] are never actually pronounced in these two words.
