Mother and son are also arguing about four valuable properties – a £1 million-plus flat in Bloomsbury Mansions, the Charlotte Street property where Thai Metro operates, and two premises in Rotherhithe and Canning Town.
The properties were mostly bought in Mr Somboonsam’s name, but his mother claims they are hers, that she paid the money and they only went in her son’s name because he convinced her she was “too old” to get a mortgage.
But Mr Strang said the son “bought those properties in his name for his benefit”.
Mr Strang added: “Mrs Walker knew and understood this. Where she made the downpayment, it was on his behalf and with money that she owed to him.
“Otherwise, he made the downpayment.”
Among Thai Metro’s most popular dishes are its £10.80 pineapple fried rice and £10.20 drunken fried rice, which Mr Somboonsam has previously called a “great hangover cure”.
Speaking after receiving the 2017 award, organised by online delivery company Hungryhouse, Mr Somboonsam said: “Before I started the business, I thought Thai food was unnecessarily overpriced.
“So we have tried to keep our prices as low as possible. We rely on repeat customers and if we can keep our prices down, people will keep coming back.”
Following an eight-day trial this week and last, the judge will give his ruling on the case at a later date.