Here is what the website says
"(Except SilkAir Destinations: Kuala Lumper, Mataram,Balikpapan, Manado, Medan, Penang, Palembang, Solo City, Surabaya, Cebu, Davao, Danang, Chongqing, Chengdu, Kunming, Shenzhen,Xiamen, Coimbatore,Hyderabad)"
I don't see HKT mentioned in the above silk air destinations at all.
Besides that little fact, there is still no way to book from HKT on the SQ site.