He studied in London with Joshua Reynolds (picture left) from 1760 until early in 1762, during which time he was also a student at St Martin's Lane Academy. Reynolds, having returned from studying the 'Old Masters' in Italy in 1752 had by 1760 established himself as a portrait painter of some renown. He worked long hours in his studio, was both gregarious and keenly intellectual and had a great number of friends from London's intelligentsia, numbered amongst whom were Dr Samuel Johnson, Oliver Goldsmith, Edmund Burke, Giuseppe Baretti, Henry Thrale, David Garrick and fellow artist Angelica Kauffmann. Because of his popularity as a portrait painter, Reynolds enjoyed constant interaction with the wealthy and famous men and women of the day and it was through Reynolds that Thomas Beach was introduced to London Society and enhanced his own reputation as a portrait painter 'who could always be relied upon to produce a good likeness'. At one time he lived in Charles Street, St James Square, removing thence to Wigmore Street.
He had settled in Bath by 1769, then a favourite resort of the fashionable world where he spent most winters, and during the 1770's he spent the summers working peripatetically in neighbouring counties gaining much employment in painting portraits and portriat groups of sitters mainly from Dorset and Somerset.
He was a member of the 'Incorporated Society of Artists' and sent two portraits from an address in Bath to the Society of Artists exhibition of 1772. He exhibited with the Society until 1783, becoming its vice-president in 1782 and president the following year. He also exhibited a total of 26 portraits at the Royal Academy mainly between 1785 to 1790 but he also submitted a portrait in 1797 of George Prince of Wales.