The group announced the move after it reported a 9% increase in like-for-like sales growth in the past year. It currently operates 11 restaurants and four cocktail bars across the north of England and Scotland.
Thai-born joint-owner and chef director Kim Kaewkraikhot - who opened the first Chaophraya in Leeds with partner Martin Stead in 2004 â' has announced the new plans as part of a wider expansion push across the UK. She said London was a priority, alongside potential other UK sites.
The group posted a turnover of £25m for the past year, and put the number of customers served at over 20,000 per week.
Kaewkraikhot commented that it was an "exciting time" for the business. She said: "It's great to be able to provide such a unique experience to diners. Every dish we choose and every recipe I develop has a special story behind it, and we can't wait to share it with even more diners."
Chaophraya runs to six sites across the UK, including in Birmingham, Liverpool, Manchester and Edinburgh. Thaikhun has so far opened in Aberdeen and Manchester, with the second site having opened in May this year.
Both serve Thai-style food, with the former a more formal offer including choices such as chicken satay, massaman curry or duck tamarind; and the latter serving Bangkok-style street food such as Moo Ping pork skewers, prawn rolls, grilled meat and fish, and a selection of street hawker-style noodles and rice.
The group also runs four bars under the brand Palm Sugar Lounge.