First off, both arts claim lineage to the palace arts of Kedah, and cite certain General-governors, or Panglima as their ancestors. Silat Cekak claims Panglima Ismail as the earliest of their lineage while in Silat Kuntau Tekpi, that honour is given to Panglima Taib. It is unknown what their status are in the official Kedah records.
Panglima Ismail was said to have served beginning 1804 and passed down the art to Panglima Tok Rashid. Panglima Taib served up to 1879 and passed down his art to his daughter, Aminah. Thus, it is possible that both Panglima Ismail and Panglima Taib met as elder and junior warriors or not at all.
Further down the line, the lineage holder of Silat Cekak beginning 1920, Yahya Said (studied from Panglima Tok Rashid) and the lineage holder of Silat Kuntau Tekpi, Zainal Abidin Endut (grandson of Panglima Taib) were both related by family and often met, although it is unknown if they ever studied from each other.
Silat Cekak and Silat Kuntau Tekpi share similar philosophies, parrying idioms and methods of striking and locking. Both await attacks in a high stance, both subscribe to close body parrying and locking.
Both arts are loosely based on the idiom of Salat, the Muslim prayer form. In Cekak, there are four basic parrying methods:
Kaedah A, based on Du'a (supplication)
Kaedah B from Qiam (standing with arms folded)
Kaedah C from Ruku' (bowing with hands on knees), and
Kaedah D from Takbir (hands in surrender position).
Tekpi on the other hand has six basic parries:
Cengkam Harimau, and
They even share many buah, similar in look and form. For example Ali Patah Atas (Cekak) and Kembang Layar (Tekpi), Kuntau Kanan Gantung (Cekak) and Ubah Haluan (Tekpi), Kilas Belakang (Cekak) and Kilas Maut (Tekpi) and in fact, even share one buah name - Pasung Kemanga, which in reality are mirror versions of each other: One locks the left arm while the other locks the right arm. The exact same buah, but reversed.
Other than this, Cekak and Tekpi differ quite a bit. Cekak has no bunga component and subscribes to modern warm-up and stretching methods, while Tekpi still has its Pelebat, an undulating dance form that serves as a traditional exercise.
The Cekak syllabus is broken down into four phases: Basics, Takedowns, Recounters and Graduation. In the first four phases there 21 buah are gradually built upon.
The Tekpi syllabus is broken down into four belts: White, Yellow, Red, Brown and Black. White and Yellow belts each have 21 different buah (which makes 42), in Red are the 5 Pukulan buah and the Tekpi exercises and usage of Tekpi in the previous 42 buah, while the Brown and Black belts are considered advanced levels for senior instructors.
Cekak has the Lading as its official weapon while Tekpi has its namesake as its normalised weapon.This sort of comparison would make a very interesting thesis or research paper, especially if we include the other claimed descendants of Silat Kedah such as Silat Kalimah, Silat Palintau, Silat Gelombang Acheh, etc, etc.
Unfortunately, undertaking such a project would take years and needs to cut across national, political and emotional boundaries. I would be open to anyone who would like to share their resources to pilot such a project.