Halal Australian beef and lamb at Siam Paragon.
I decided to post this as my response to one of the blog visitors, who has just moved to Bangkok from Jakarta. Thank you for visiting and I'm glad that you found it informative.
To start off, halal chicken and beef can be found at almost all big wet markets in Bangkok but dont be surprised as some smaller markets have them, too. Besides the wet market, halal chicken are also available at the Home Fresh Mart (supermaket at the Mall chain stores & Siam Paragon) and TESCO Lotus. The Home Fresh Mart also sells halal processed chicken such as chicken cocktail, salami etc. Please beware when buying from TESCO as not all is Halal. Make sure you check the label before purchasing. Some CP chicken are halal, too, as they come from farms different from the non-halal ones. Halal mutton and lamb are available at Bak Rak Market and in front of Masjid Ban Ooo, behind Shangri-La Hotel, near Saphan Taksin BTS Station.

The
French-Thai Butchery has its main store at Sukhumvit Soi 33 (near Villa Market). Besides that it also has its counters at
Villa Market all around Bangkok. The French-Thai Butchery supplies halal grade 1 beef. You have the choice to pick any parts of the beef which you like based on the chart provided. Unfortunately, they do not carry lamb.

Halal bread by S.T. Bakery sold at certain 7-Eleven stores.
Halal healthy breakfast cracker is available at Tesco Lotus.
Halal organic cereal bars at Villa Market.
Chicken sold at Home Fresh Mart which is available at Siam Paragon and all The Mall supermarkets.

Allowrie butter and cheese produced in Thailand are halal, but the ones imported from Australia are without the Halal certification. There are a few other brands with the Halal certification. There's even halal mozzarella cheese at Home Fresh Mart.
Caroline mozzarella and samsoe cheese
Halal Mascarpone cheese by Caroline are available at Villa Market.
Soft tofu
Halal ready to cook beef and chicken by Kin Sun: available at the Mall supermarkets
Halal yellow noodles at Top's Market
Halal Australian beef and lamb burgers are available at the Emporium, Sukhumvit Soi 24.
There's a Halal minimart called Halal Express at Minburi, on the way to Nong Chok.
Fresh beef and lamb cuts are available at
Sindhorn Steak House minimart on Ramkhamhaeng Road.
Fresh beef, mutton and lamb are available in the morning at
Silom Soi 20 Market &
in front of Masjid Ban Oou, behind Robinson's Bang Rak.
Ramly burger and chicken sausage are available at
Carrefour Rama IV and a
Muslim shop adjacent to Fahana Italian Restaurant on Rama IX Road.
p.s.I shall keep updating this post with current info from time to time.