Halliday & Matthiessen (2014: 522-3):
This combination of a verbal process with ‘reporting’, although we are treating it as logically subsequent to quoting, being arrived at by analogy with the reporting of a mental process, is the normal way of representing what people say, in most registers of English today. The opposite combination, that of a mental process with ‘quoting’, is also found, although considerably more restricted. Here a thought is represented as if it was a wording, for example
I saw an ad in the paper for dachshunds, and I thought ‘I’ll just inquire’ – not intending to buy one, of course.
||| I thought || ‘I’ll just inquire’ |||
||| ‘The gods must watch out for Kukul,’ || he thought to himself. |||
||| So I figured ||‘Well, then obviously it’s going to be a nineteenth-century American novel’. |||
||| ‘When all’s said and done,’ << he reflected, >> ‘she hasn’t had much chance.’ |||
The implication is ‘I said to myself ... ’; and this expression is often used, recognising the fact that one can think in words. Only certain mental process verbs are regularly used to quote in this way, such as think, wonder, reflect, surmise.