What are wh-questions in Thai?

Content/wh-questions are one of fundamental clausal structure that is distinctive to and ubiquitous of human language . Based on parameterization, in-situness is a typical structure of wh-questions in East and Southeast Asian languages (e.g., Thai, Lao, Vietnamese, Burmese, Mon-Khmer, inter alia). In my PhD project, I'm interested in the syntax of wh-questions in Thai (my native tongue). Examples of Thai wh-questions are given below:

1) a. dɛkdɛk  kɪn  ʔàraj 

child.child eat what

       'What did the children eat?'

b. dɛkdɛk  mâj kɪn  ʔàraj 

child.child NEG eat what

(I) 'What didn't the children eat?'

(II) 'The children didn't eat anything.'

c. dɛkdɛk  kɪn  ʔàraj mǎj 

child.child eat what Q

'Did the children eat something?'

One of the intriguing puzzles arising in my mind is why we get different readings of (a-c), despite the identical wh-word 'ʔàraj'. This means the wh-word 'ʔàraj' doesn't have intrinsic meaning on its own, but it is derived or licensed by something else. 

There are, to my best knowledge, two existing proposals to account for this phenomena in Thai. Panpothong (1997) produced a very brief paper entitled 'Is there wh-movement in Thai?', and her response is positive. She argues that there is covert wh-movement in Thai, along the same line with Huang 1982. The evidence for her analysis comes from island-sensitivity of thammay 'why' and presence of weak crossover effect (WCO). If Panpothong were correct that a why-adjunct undergoes covert movement, why is focus intervention effect detected in a 'why'-question? cf. Beck 1996, 2006 and Pesetsky 2000 (and its descendants  e.g., Cable 2010,  Kotek 2014, 2019) for covert movement.

On the other hand, Ruangjaroon 2005 provides a wh-binding construal analysis of wh-questions. In her analysis, wh-questions are derived by probe-goal matching relation (which is on its essence similar to the previous analyses of Reinhart 1998, Pesetsky 1998, a.o.). However, according to Ruangjaroon's (2005) analysis, (1b) only yields only the NPI reading of 'ʔàraj', which a bunch of the Thai speakers also can access the interrogative reading of (1b). While the range of the Thai wh-questions cast much doubt on the former analysis, the latter leaves remaining puzzles to us and looks over some crucial data. 

Primary part of my main project investigates the Thai wh-questions. My claim is that that the Thai wh-questions are derived by an in-situ strategy of interpretation such as unselective binding. The Q operator occupies at a topmost position of clausal spine and bind a wh-variable with an interrogative force in a downward fashion. The empirical motivation for my analysis is primarily drawn from island-insensitivity and presence of focus intervention effect.  WCO effects and parasitic gaps do not tell us whether it be covert movement or non-movement derivation under the Thai wh-questions.  After all, closer examination upon the wh-questions gives me insight into the syntax of single and multiple sluicing in Thai.