The stakes are high and the public has high expectations for the anti-graft agency's probe into how Deputy Prime Minister Prawit Wongsuwon acquired a luxury watch and expensive diamond ring and whether he concealed those items in previous asset declarations.
Let's be clear. It is not just the credibility and trustworthiness of Gen Prawit and the military regime that is at stake here. The National Anti-Corruption Corruption (NACC) has much to gain or lose from a case it has described as being "not complicated".
Since the National Council for Peace and Order (NCPO) took over in 2014, corruption has been a key problem it has vowed to tackle. The goal sounded promising but was later hurt by several conflicts of interest and corruption allegations made against regime members and people in their families.
The NACC's apparent lack of political impartiality merely rubs salt into the wound.
With five of its nine commissioners chosen by NCPO-appointed lawmakers in late 2015, the agency already faced an uphill task in proving its independence and integrity when investigating allegations against regime members. Sadly, the agency has failed the public in many of these cases.
The Prawit case gives it an extraordinary test. He is not just second in the NCPO's line of command. He is also a former boss of the current NACC president, Pol Gen Watcharapol Prasarnrajkit. The latter served as Gen Prawit's secretary-general after the May 2014 coup, handling political affairs for him.
Scepticism has grown over whether this personal connection will influence the probe. This time, the NACC cannot afford to let the public down.
The agency gave Gen Prawit this week a 30-day deadline to submit information on the acquisition of the two items. When revealing its findings, the NACC ought to be explicit and clear.
It cannot resort to euphemisms or roundabout explanations, like when it and other agencies dismissed kickback allegations involving the army's 1-million-baht Rajabhakti Park project last year.
Nor can it afford to show a lack of progress, like its fact-finding mission into a conflict of interest allegation involving 97 million baht in contracts of the 3rd Army Region.
They were won by a company whose major shareholder is the son of former defence permanent secretary Preecha Chan-o-cha. Gen Preecha is the younger brother of Prime Minister Prayut Chan-o-cha.
Another NACC probe that has advanced at a snail's pace involves an allegation against Gen Prawit's younger brother, ex-police chief Pol Gen Patcharawat Wongsuwon. This was over the unusual amount of wealth he accumulated while holding public office.
Since a panel was appointed to probe the case in 2014 no progress has been made. In August, the Isra News agency revealed that the NACC had blocked the public's access to information about the case on its website.
Such a lack of transparency is intolerable. It must not occur in the Prawit case. As NACC president, Pol Gen Watcharapol needs to refrain from involving himself at any level in this probe against his former boss to ensure its integrity and transparency.
The NACC also needs to engage external observers or investigators who have no connection with the regime or itself.
After the 30-day period, the agency is duty-bound to reveal the full story of Gen Prawit's explanation to the public.
A patchy narrative cannot be accepted given Gen Prawit's seniority. His roles and influence in the state's approval and spending regarding megaprojects are highly significant.
This case concerns more than just the financial value of a watch and a ring. It relates to the responsibility and transparency we entrust to a member of government, such as Gen Prawit, and how these values must be respected.