Bilahari has no love for Thum at all (despite his own growing role as the Emperor's tailor) - he has repeatedly called Thum out as an "attention seeking historian" (of course his own remarks on FB as a retired statesman now should not be construed as such) - Bilahari's remarks most recently on 27 July:
"
The attention seeking academic is at it again: he objects to the 1964 riots being characterised as 'race riots' because they were the consequence of political manipulation and manoeuvres. Yes of course they were -- the intention was to put Singapore in its place by intimidation -- but so what? Does he think that the manipulation and manoeuvres would have succeeded in igniting violence if the racial situation had not been already fraught? And if we do not call them 'race riots' what do we call them? 'Political riots'? How does that change the fact that the riots were between Malays and Chinese and not, say, between Hokkiens and Teochews or between Martians and humans. Of course, context is important but one should not use that as an excuse to torture facts to make them submit to strained interpretations that are either intended to seek attention or advance a political agenda. Braying white just because the established interpretation is black is not critical thinking. History is too important to be so abused."
Please correct me but I am ignorant of any other historian on local history has outwardly challenged Thum's analysis and interpretation of Singapore's history - Bilahari has great disdain for academics and great adoration for his own views no doubt - but as you pointed out, if access to archival material is not available then how complete is the understanding of historical matters. Even when personally involved the extent of the dynamics can be lost.
I sense Thum being an Oxonian also irritates the likes of Bilahari. He also made remarks against Thum at the now infamous Cambridge lecture on 31 Oct 2015:
"
Mr Bilahari's topic was "Lee Kuan Yew's cast of mind and its lasting influence". As I leaned forward to listen, I had not bargained to be in for some unpleasant surprises.
To my amazement, Mr Bilahari departed from his prepared transcript at least twice to take two digs at Dr Thum - to make it clear to the audience that he was not in agreement with Dr Thum’s point of view.
On Dr Thum’s view that the PAP government was intolerant of dissent, Mr Bilahari argued that since Dr Thum was able to express his dissenting views about Mr Lee’s political role, then Dr Thum can’t be right to complain that the PAP government was intolerant of dissent.
I was taken aback. I failed to see the logic of Mr Bilahari's reasoning. Dr Thum had expressed his dissenting views to an international audience at an overseas conference, not in Singapore. Has Dr Thum been free to express his dissenting views in Singapore without adverse repercussions?
Mr Bilahari's second swipe at Dr Thum was more caustic. He called Dr Thum "a young academic trying to make a name for himself" - implying that Dr Thum was propagating an alternative version of Singapore’s history so as to draw attention to himself.
Some in the audience booed Dr Bilahari on hearing his ungracious words against Dr Thum.
I was shocked - and ashamed - that a high ranking diplomat would deem fit to speak against a fellow Singaporean speaker at an overseas conference in front of an international audience.
By trying to attack Dr Thum's credibility, Mr Bilahari only succeeded in proving Dr Thum right about the PAP Government's intolerance for dissenting views.
But there was one more unhappy surprise in store for me."
http://jeannettechongaruldoss.blogspot.sg/2015/12/bilahari-kausikan-loose-and-at-large.html