sentence-end-without-period

sentence-end-without-period is a variable defined in `paragraphs.el'.
Its value is

nil

• This variable is safe as a file local variable if its value
  satisfies the predicate `booleanp'.

Documentation:
Non-nil means a sentence will end without a period.
For example, a sentence in Thai text ends with double space but
without a period.

This value is used by the function `sentence-end' to construct the
regexp describing the end of a sentence, when the value of the variable
`sentence-end' is nil. See Info node `(elisp)Standard Regexps'.

You can customize this variable.