The British no2 now has just one win in eight matches, coming against world no441 Giuliana Olmos in the Billie Jean King Cup.
Watson has struggled with injuries and was wearing strapping around her shoulder during a 6-4 7-5 loss to 93rd-ranked Kazakh Diyas.
Earlier, birthday girl Iga Swiatek beat friend Kaja Juvan of Slovenia 6-0 7-5 to begin her French Open title defence.
Celebrating her 20th birthday, the Pole did not seem keen to spend too much time on court and came out all guns blazing from the start on a windy day in the opening match at Court Philippe-Chatrier.
Swiatek treated herself to a 6-0, 7-5 victory — her eighth straight-sets win in a row at Roland Garros, having also not dropped a set in winning the trophy last year as an unseeded 19-year-old. She will face either Shelby Rogers or Rebecca Peterson later in the week.